converting ana array to a hash

hotshot has asked for the wisdom of the Perl Monks concerning the following question:

Hi guys !

A simple one. How can I convert an array of n elements to a hash with those n elements as keys? (the values are not important to me).

Second one. I have to run on the above hash as follows:

while (1) {
  for $key (keys(%myhash)) {
    if (&isPassTest()) {
      delete($key);
    }
  }
}
[download]

like that I run on a decresing hash %myhashtill every element passes the test and the hash is empty. Will it work or removing elements while running on the hash can cause problems of some sort?

Thanks.

Hotshot

Edited: ~Wed Jul 24 15:26:45 2002 (GMT) by footpad: Added missing </code> tag

Comment on converting ana array to a hash Download Code

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Re: converting ana array to a hash by broquaint (Abbot) on Jul 24, 2002 at 13:17 UTC
How can I convert an array of n elements to a hash with those n elements as keys? Like so `my @array = qw( foo bar baz quux ); my %hash = map { $_ => 1 } @array;` [download] Will it work or removing elements while running on the hash can cause problems of some sort? You need to change `delete($key);` [download] to `delete($myhash{$key});` [download] And assuming `isPassTest()` is performing the tests correctly it should work fine, although you will need to exit the loop at some point e.g `last if 0 == keys %myhash;` HTH `_________ broquaint`	[reply] [d/l] [select]
Re: converting ana array to a hash by jmcnamara (Monsignor) on Jul 24, 2002 at 13:26 UTC
The best way to do this is via a hash slice. In the first example the hash values will all be `undef`. To assign a value to all the keys you can use the second method: `my @a = (1..9); my %h; # hash slice @h{@a} = (); # Same thing but sets each value to 1 @h{@a} = (1) x @a;` [download] Hash, and array, slices are explained in perldata. -- John. It is worth noting that the assignment in the first example is only to the hash value associated with the first element of the array.	[reply] [d/l]
Re: converting ana array to a hash by giulienk (Curate) on Jul 24, 2002 at 13:19 UTC
1)`my %hash = map {$_ => 1} @array;` 2) you got to use `delete $myhash{$key}` to erase it from `%myhash` and then you're gonna have no problem as the `for` loop iterates over the elements of the anonymous array created by `keys(%myhash)` Update: broquaint can type faster than me ;) `$\|=$_="1g2i1u1l2i4e2n0k",map{print"\7",chop;select$,,$,,$,,$_/7}m{..}g`	[reply] [d/l]
Re: converting ana array to a hash by simeon2000 (Monk) on Jul 24, 2002 at 13:22 UTC
First one is pretty simple: `my %hash = (); my @array = qw /fred jim john joe/; @hash{ @array } = @array;` [download] ... since you're not worried about the values ;) "Falling in love with map, one block at a time." - simeon2000	[reply] [d/l]